A drum magazine is a type of firearms magazine that is often cylindrical in shape, like a drum.
Instead of rounds being stored flat, as in a more common box magazine, rounds in a drum magazine are stored in a circle around the center of the magazine, facing the direction of the barrel. Drum magazines for rimless ammunition are typically driven by a single hub and a telescopic shaft.
The advantage over traditional box-shaped magazines is that a drum magazine can carry much more ammunition, often two to three times that of a box magazine, without making it too big to be impractical to carry. The downside to drum magazines is they increase the overall weight of the weapon in which they are being used, and they are more prone to jamming because of their more complex internal geometry. When the mainspring is unwound so the operator is not having to overcome a strong biasing force when loading new cartridges, sometimes the telescopic shaft is moved out of contact with the stack of cartridges. The absence of pressure on the stack of cartridges can enable one or more cartridges to become misaligned within the interior of the drum magazine. As a result, the magazine can become jammed and unable to feed cartridges to an attached firearm once the mainspring is wound and the telescopic shaft exerts pressure upon the stack of cartridges.
Therefore, a need exists for a new and improved drum magazine that supports the stack of cartridges during loading even when the telescopic shaft does not contact the stack of cartridges. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the drum magazine according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing the additional capacity of a drum magazine while preventing the ammunition from jamming during the loading of new cartridges.